BD8643FV-E2 Rohm Semiconductor, BD8643FV-E2 Datasheet - Page 5

• Manufacturer Part Number: BD8643FV-E2
• Description: IC SWITCH REG 3A W/FET 20SSOP
• Manufacturer: Rohm Semiconductor
• Series: -r
• Type: Step-Down (Buck), PWM - Current Moder

Specifications of BD8643FV-E2

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 1 V ~ 12.6 V
• Current - Output: 3A
• Frequency - Switching: 100kHz ~ 600kHz
• Voltage - Input: 4.5 V ~ 18 V
• Operating Temperature: -20°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 20-LSSOP (0.240", 6.10mm Width)
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

●Operation description
BD8643FV
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www.rohm.com
1 Enable control
The device can be controlled ON/OFF by EN terminal (15 pin) voltage.
An internal circuit starts when VEN reaches 1.4V.
When standing up of VIN is too steep (1msec or less), a defective start might be caused according to the state of Pascon
between GND substrate pattern and power supply-when the terminal EN is short-circuited to the terminal VIN and it is used.
2 Soft start time set function
As for BD8643FV, output can do soft start without overshoot by charging soft start capacity (C
SS/DELAY (9 pin) and GND (10 pin) terminal.
Also, soft start time (tss) can be set by setting soft start capacity (C
3 OSC oscillation frequency setting function
The output oscillation frequency can be set by connecting resistance between terminal RT (13 pin) and GND
(range = 100kHz – 600kHz)
The relation between RT terminal resistance and the oscillation frequency follows Fig.13.
Output setting voltage
EN terminal
SS terminal
10000
1000
100
10
1
Fig.12 ON/OFF transition wave form in EN controlling
Fig.13 Oscillation frequency setting by RT resistance
V
V
V
V
SSCLM
V
V
ENL
ENH
SSTH
V
EN
SS
O
0
0
0
10
t
SS
5/13
RT[kΩ]
SS
) arbitrarily.(Refer to 5-2 soft start time setting method)
100
1000
SS
) connected between
Technical Note
2010.09 - Rev.A